Background <p>Nutrition is an important component for the developing swimmer and may be important to determine future success in the sport. Education is a key driver of facilitating changes in nutritional behaviour, but little is known about how this applies in practice among trained young swimmers. The purpose of this study therefore was to explore the impact of a nutrition education programme on dietary intake and nutrition knowledge in trained young swimmers. Fifteen participants aged 16 ± 3 years completed a 21-week education programme delivered via seven presentations and meal planning support. Energy, carbohydrate (CHO), protein, fibre, calcium, and iron intake were estimated in eight participants using the remote food photography method, alongside assessment of nutrition knowledge in fourteen participants using the Nutrition for Sport Knowledge Questionnaire, which were both conducted prior to and following the intervention.</p> Results <p>There was no change in energy, protein, or fibre intake following the intervention. Absolute CHO intake (<i>p</i> = 0.021), iron (<i>p</i> = 0.016), and calcium intake (<i>p</i> = 0.022) were significantly lower following the intervention. Nutrition knowledge was significantly greater following the intervention (57.21 ± 15.86% vs. 72.14 ± 12.44%; <i>p</i> = 0.004) with greater nutrition knowledge positively associated with greater dietary fibre intake (β = 0.50, <i>p</i> = 0.007).</p> Conclusions <p>These findings highlight the complex nature of facilitating changes in dietary intake in young swimmers and suggest that improvements in knowledge do not always translate to improved dietary practices.</p>